Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

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Sun 4:43 PM —Forecast Review —We had some sun but then considerable clouds with some sprinkles in NJ during the afternoon. Temperatures reached 73º at Philadelphia airport around 2:30 PM, higher than my forecast or any model forecast. Here’s the RTMA (near actual) temperatures at 4PM—
4 PM (20z) RTMA actual temperatures. Fine Black Contours are near ground (2m) temperatures in 1º increments. (Click on image for a larger view.)

Yet Another Forecast Change

Posted Saturday 03/07/26 @ 5:01 PM — Today’s models have reverted back to previous forecasts: a weak cold front (really a wind shift) will fall apart as it approaches the Delaware Valley with minimal showers. Several models show some light rain (sprinkles) in the morning. A few show some increased shower activity in the mid afternoon, mostly in Southern NJ and eastward.

The RRFS shows clouds through 3 PM, then clouds slowly lift. Overall, a poorly defined forecast. (The NBM’s temperature standard deviation is now only 2º.)

High temperatures range from the NBM (62º ± 2º) to the ECMWF (70º in Philadelphia, 67º Blue Bell) and the ECMW-AI ( 68º) GFS (68º Philadelphia, 66º Blue Bell.) I think we’re going to be just short of 70º at best.)

Weekend Forecast Update

Posted Saturday 03/07/26 @ 10:31 AM — There was a reason I emphasized uncertainty in yesterday’s forecast. (The NBM large standard deviation on temperature gave it away.) This morning was more damp with mist than expected. Unfortunately, this morning’s models continue with the low clouds (perhaps with some bright spots mid day and late afternoon) with the fog returning this evening.

Current conditions (Water Vapor) show the stalled front still to our south.

Water Vapor image this morning with superimposed RAP model MSL pressure (black contours), GFS/NAM potential vorticity contours (yellow & violet fine contours) with MRMS Radar and surface wind barbs, (Click on image for a larger view.)

The latest GFS continues to show some showers Sunday afternoon between noon and 3 PM.

Change in the Forecast

Originally Posted Fri 5:22 PM —The weekend had been looking much better until today’s model runs. Instead of a nice warm day on Sunday, a cold front will move through with rain. The developing disturbances are outlined in the current water vapor image—

Current satellite water vapor image with superimposed RAP model 500-1000 mb thickness lines (yellow), Mean Sea Level Pressure isobars (black contours) potential vorticity (fine violet contours) with superimposed MRMS RADAR. Boxed area shows a potential disturbance moving up from the south and joining in with a cold front moving through. (Click on image for a larger view.)

While Saturday appears to be cloudy but dry, the front will approach early Sunday. Here’s Saturday at 7 PM—

12z ECMWF-AI forecast for Saturday at 7 PM. Cold front to our west. Impulse developing in Alabama. (Click on image for a larger view.)

By Sunday afternoon, the front and the low pressure system is on top of us.

12z ECMWF-AI forecast for Sunday 2 PM (Click on image for a larger view.)

This is a significant change in the forecast, where previously, this front had been expected to weaken with little in the way of precipitation. Not all models are on-board with this wet forecast, but I’m leaning towards the ECMW-AI, ECMWF NAM-NEST and GFS.

Saturday Forecast

Continued low clouds. There may be partial clearing, especially south of the city, in the mid to late afternoon. Winds 5-10mph

NBM high temperatures: Blue Bell, PA 54º Philadelphia, PA 57º
High Uncertainty (based on standard deviation): ± 4º

Sunday Forecast

Some bright skies possible very early. then cloudy with showers by late morning. Showers through 3 PM, then some sun by 5 PM. Gusty winds with the showers and the front early afternoon.

NBM high temperatures: Blue Bell, PA 64º Philadelphia, PA 66º
Moderate Uncertainty (based on standard deviation): ± 3.0º

With temperatures again showing such large standard deviations, it suggests that this forecast is more uncertain than usual. Errors and changes are certainly possible.